The need to clean up our environment has led to the development of new methods and apparatus designed to solve the problems encountered in the cleanup effort. A major environmental problem is the contamination of surface and subsurface soils. This type of contamination can occur by either dumping contaminants on the surface or by leaking underground storage tanks. Perhaps the most widespread form of contamination is caused by leakage from underground tanks in the gasoline distribution industry. One method of cleaning up this type of pollution involves the use of a vapor extraction system (VES). A typical VES uses slotted and screened piping buried within contaminated soil and in turn connected to a manifold and blower. The blower produces a vacuum (a pressure lower than atmospheric, measured in inches of water column) in the piping system, thereby withdrawing volatile contaminant vapors from within contaminated soils. The soil being treated can be either subsurface soil or soil that has been excavated into a stockpile.
A significant amount of moisture is withdrawn along with the volatile vapors being extracted from the soil. In order to insure that there is no moisture or condensate build up within the system that could damage the VES blower, a condensate trap or collector is used to safeguard the system. Generally speaking, the blower is driven by an electric motor that can be severely damaged by condensate. The blowers are also susceptible to corrosive damage caused by condensate. In order to increase reliability and reduce costs of a VES, it is important to protect the blower from condensate.
A typical condensate collector consists of one or more 35 or 55 gallon drums. Each drum normally has an air/vapor inlet on the side of the drum which is connected to the VES manifold: an air outlet at the top of the drum that is connected to the vacuum pressure side of the VES blower; and a manual condensate drain valve at the base of the tank which is used to drain any condensate that collects within the tank. In the majority of applications the drums fill with condensate at a rate that requires service intervals to be based on draining the drums rather than on other factors. Since the length of the service interval directly effects the cost of running the VES, the longer the interval, the lower the cost. If the drums are not emptied on a short enough time interval, the system may shut down between site visits. A VES system shuts down due to the loss of suction created when a high condensate level in the tank activates an automatic shutoff on some of the condensate tanks. Other systems fail due to condensate passing through condensate tanks not equipped with an automatic shutoff, thereby damaging the blower.
A condensate collector automatic shutoff valve is an internal valve connected to the air outlet connection through a bulkhead fitting. The automatic shutoff includes a two inch inside diameter cylinder suspended from the tank's lid and a floatation ball within the cylinder that rises as the condensate level rises in the collector unit. At a predetermined level of condensate, the floatation ball will engage the suspended pipe and automatically block the transfer of condensate to the blower, thereby removing the effect of condensate induced blower damage. The vacuum level at which the automatic shutoff would activate is typically 15 inches of water column.
The collectors currently used also corrode on the inside, producing rust flakes which foul the manual or check valve over time. Iron bacteria in the tanks can also foul the valves, causing them to malfunction. When a check valve malfunctions, preventing the tanks from draining properly, the service interval must be shortened in order to ensure that the system continues to operate.